Frenzelsberg, Mountain summit in Seifhennersdorf, Germany

Frenzelsberg is a mountain in eastern Upper Lusatia near the Czech border, rising to approximately 474 meters. The slopes are covered with mixed forest and meadows, crossed by several marked hiking trails that connect to nearby attractions.

In 1770 the Rumburg estate took rock from the hill for the road running on the Czech side of the border. A tavern opened on the wooded summit in 1877, after which the hill became a popular excursion destination. Workers held their first May Day celebration there in 1890, followed by gatherings in 1896 and 1930. After the First World War the local group of the Touristenverein "Die Naturfreunde" converted the hut into a Naturfreundehaus with a youth hostel, which was seized in 1933 after the Nazi takeover and later decayed.

Older residents of Seifhennersdorf regard the Frenzelsberg as a weather mountain, and local lore holds that its basalt, called "Blue Stones", wards off misfortune. A legend tells of a treasure cave on the summit, and a newer tale of a war chest being raised there. The wooded summit also hosted the workers' first May Day celebration in 1890.

The hike is manageable for people with average fitness and takes about three hours for the round trip from the Karasek Museum parking area. Spring through autumn offers the best conditions, with dry trails and clear views from the summit across the border landscape.

The basalt from the small abandoned quarry on the Frenzelsberg, a nepheline tephrite, was used internationally as the reference type for the nepheline-tephrite group of basalt. Locals call the rock "Blaue Steine" and, according to folk belief, it is said to ward off misfortune. The quarry's columnar structure is still clearly visible.